LTE (long term evolution), also popularly called 3.9G, has a 100 Mbps data download capability, and is considered as a mainstream technology for evolution from 3G to 4G. LTE study includes some parts that are universally considered to be very important, for example, waiting time shortening, a higher user data rate, system capacity and coverage improvement, and operating expense reduction.
An LTE project of a 3GPP (3rd generation partnership project) is the largest new technology research and development project started by the 3GPP in recent two years. This technology with OFDM/FDMA (orthogonal frequency division multiplexing/frequency division multiple access) as a core may be considered as a “quasi-4G” technology. Major performance objectives of the 3GPP LTE project include: to provide a peak rate of downlink 100 Mbps and uplink 50 Mbps under a 20 MHz spectrum bandwidth; to improve the performance of a cell edge user; to increase a cell capacity; to reduce a system delay, so that the unidirectional transmission delay inside a user plane is less than 5 ms, and the duration of migration of a control plane from a sleep state to an activated state is less than 50 ms, and the duration of migration from a resident state to the activated state is less than 100 ms; to support the cell coverage with a radius of 100 km; to provide an access service greater than 100 kbps for a user moving at a high speed of 350 km/h; to support paired or unpaired spectrums, and flexibly configure multiple bandwidths from 1.25 MHz to 20 MHz.
WLAN (wireless local area networks) is a system that performs data transmission using a radio frequency (RF) technology. This technology is a supplement of a wired local area network, and achieves the objective of network extension, enabling the wireless local area network to make use of a simple access architecture to allow a user to achieve an unobstructed network with no network cable or distance limit through it. As a standard of the WLAN, WiFi (wireless fidelity) is a wireless network formed by an AP (Access Point) and a wireless network interface card. The AP, generally called a network bridge or an access point, serves as a bridge between a traditional wired local area network and a wireless local area network. Therefore, any user terminal equipped with a wireless network interface card may share resources of a wired local area network and even a wide area network through an AP. Its working principle is equal to a HUB or a route imbedded with a radio transmitter, while the wireless network interface card is a client device responsible for receiving signals transmitted by the AP.
Currently, for an EPS (evolved packet system), an air interface adopts an LTE technology, which is implemented by deploying an eNodeB (evolved Node B or evolved base station). However, when a UE (user equipment) uses a service in the EPS system, the user equipment may implement transmission only through the LTE air interface of the eNodeB deployed on a network.
With the increase of bandwidth demands, a network operator needs to increase the transmission bandwidth over the air interface by deploying more LTE base stations and narrowing the coverage, which causes increase of investment costs and maintenance costs. Therefore, to satisfy increasing mobile bandwidth demands and make up for the regret of insufficient transmission bandwidth over the LTE air interface, offload the data that needs to be transmitted over the LTE air interface to other available access technologies needs to be taken into consideration.